Method and apparatus for handoff between a wireless local area network (WLAN) and a universal mobile telecommunication system (UMTS)

ABSTRACT

Apparatus and method for providing an automatic handoff process of a dual-mode user equipment (UE) from either a wireless local area network (WLAN) to a universal mobile telecommunications system (UMTS) or from a UMTS to a WLAN. Handoffs may be initiated by the UE, based upon user preference, signal quality, comparison of location coordinates of the UE and the system to be switched to or signal quality. The available channels of one system may be sent to the UE by the other system or the UE may monitor channels of the system to be switched to and lock on to one. The handoff may also be initiated by the UMTS, the selection being power-based.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 11/111,569, filed Apr. 21, 2005, which is a continuation of U.S. patent application Ser. No. 10/294,065, filed Nov. 14, 2002, which claims priority from U.S. Provisional Application Ser. No. 60/393,413, filed Jul. 2, 2002, which are incorporated by reference as if fully set forth.

BACKGROUND

The present invention relates to WLAN and UMTS systems. More particularly, the present invention relates to apparatus and techniques for automatic handoff between WLAN and UMTS Systems.

The triggering of a handoff process between a UMTS System and a WLAN System can be performed by a manual handoff process initiated by the user wherein the user knows the existence of the WLAN coverage in the current geographic location and switches “on” its WLAN connection.

Nevertheless, it is extremely desirous to provide an automatic handoff process.

SUMMARY

The present invention is characterized by providing automatic handoff techniques which may be either UE-initiated or system-initiated.

Regarding-UE initiated techniques, the UE detects the existence of a WLAN footprint and initiates the handoff (HO) process based on a user preference. Alternatively, the UE may track the locations of WLAN coverage areas and initiate the HO process within a specific range from the WLAN.

System initiated techniques include the following:

Power measurements requested from the UE by the system which include a set of all WLAN frequencies. The system initiates the HO procedures based on a set of criteria which includes the mobility of the UE and the desired applications, when the UE is within the WLAN coverage area.

As another embodiment, the system tracks the UE location and initiates the HO procedures based on a set of criteria, including mobility of the UE and the requested applications, when the UE is within the WLAN coverage area.

BRIEF DESCRIPTION OF THE DRAWING(S)

The present invention will be understood from consideration of the detailed description and drawings wherein like elements are designated by like numerals, and wherein:

FIG. 1 is a flow diagram showing a UE initiated handoff from a UMTS to a WLAN.

FIG. 2 is a flow diagram showing a UE initiated handoff from a UMTS to a WLAN which is location based.

FIG. 3 is a flow diagram showing a UE initiated handoff from a UMTS to a WLAN which is power based.

FIG. 4 is a flow diagram showing a UE initiated handoff from a UMTS to a WLAN, which is power based with no broadcasting.

FIG. 5 is a flow diagram showing a UE initiated handoff from a WLAN to a UMTS employing a WLAN broadcast technique.

FIG. 6 is a flow diagram showing a UE initiated handoff from a WLAN to a UMTS where there is no broadcast.

FIG. 7 is a flow diagram showing a UMTS system initiated handoff of a UE from a UMTS to a WLAN, which is power based.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A UE-initiated handoff from an UMTS12 to a WLAN14 is shown in the flow diagram of FIG. 1 wherein, at step S1, the system (UMTS) broadcasts a list of WLANs available within the cell in which the UE10 is located. The UE10 receives and stores a list of all WLANs available within that cell, at step S2. At step S3, the UE10 requests the locations of WLANs available within the cell, said request being based upon user preference. At step S4, the UE10, as it is moving, compares its current coordinates with the coordinates of those WLANs stored. At step S5, a determination is made as to whether the UE10 location and the WLAN14 location are within a preset limit. If not, the program jumps, at step S5A, back to step S4. In the event that the UE10 and WLAN14 locations are within the preset limit, the program jumps, at step S5B, to step S6 whereupon the handoff (HO) procedure is initiated.

FIG. 2 shows a more detailed UE—initiated handoff technique which is location based wherein the procedural steps take place between UE 10, UMTS 12 and WLAN 14.

At step S1, UE 10 listens to the broadcast control channel (BCCH).

UMTS 12 broadcasts a list of WLANs available, at step S2. At step S3, UE 10 receives and stores the WLAN list and, based upon user preset preference, UE 10 initiates acquisition of the locations of the preferred WLANs and, at step S4, requests that UMTS 12 provide the locations of the preferred WLANs. At step S5, UMTS 12 retrieves the location information and provides UE 10 with a list of the WLANs and their associated locations, at step S6.

At step S7, UE 10 monitors the location information and initiates a handoff (HO) when UE 10 is in the range of the WLAN coverage, UE 10 initiating WLAN service to WLAN 14, at step S8.

WLAN 14, at step S9 authenticates the UE 10 through an interchange of information with UMTS 12, at step S10 and, depending upon the interworking case, at step S11, grants access to UE 10 and may provide a new internet protocol (IP) address depending on the interworking case.

UE 10, at step S12, initiates the handoff to the WLAN through UMTS 12, data being routed through a communication link between UMTS 12 and WLAN 14, at step S13.

UMTS 12, at step S14, provides a message to UE 10 that the handoff process is complete and, at step S15, services are resumed on the WLAN system 14 between UE 10 and WLAN 14.

FIG. 3 shows another technique for a UE initiated handoff from a UMTS 12 to a WLAN 14, UE 10′ having communication capability with the UMTS 12 at 10 a′ and with the WLAN14, at 10 b′.

At step S1, UE 10′ listens to the broadcast channel (BCCH), UMTS 12, at step S2, broadcasting the list of available WLANs in the channel.

UE 10′, at step S3, receives and stores the WLAN frequency list. UE 10′ initializes radio unit 10 b′ at step S4 and, at step S5, transmits the WLAN frequency list to 10 b′. The WLAN receiver 10 b′ monitors the WLAN channels, at step S6 and, at step S7, locks onto a WLAN channel and initiates WLAN service with WLAN 14, at step S8.

At step S9, WLAN 14 authenticates the UE 10′ through an interchange of information with UMTS 12, at step S10. At step S11, WLAN 14 grants access to WLAN service and may allocate a new IP address depending upon the interworking case. The handoff is initiated between 10 b′ and 10 a′ at step S12 and 10 a′, at step S13, initiates the handoff to WLAN 14 through UMTS 12 which routes data to WLAN 14, at step S14.

UMTS 12, at step S15, alerts unit 10 a′ that the handoff process is complete and 10 a′, at step S16 alerts 10 b′ that the HO process is complete, whereupon services on the WLAN system are resumed between UE 10′ and WLAN 14, at step S17.

FIG. 4 shows a UE-initiated handoff technique from UMTS 12 to WLAN 14 wherein UE 10′ shown in FIG. 4 is similar in structure to the UE 10′ shown in FIG. 3. In this embodiment, the handoff is power based and no broadcasting takes place.

The packet switched (PS) is attached, at step S1, from unit 10 a′ and the power at 10 b′ is turned on, at step S2. Unit 10 a′, at step S3, initializes the radio unit of 10 b′, whereupon 10 b′, at step S4, has its receiver monitor WLAN channels, locking onto a WLAN channel, at step S5, and initiating WLAN service with WLAN 14, at step S6.

WLAN 14 authenticates UE 10′, at step S7, through an authentication procedure with UMTS 12, at step S8, and grants access to WLAN service at step S9 and may allocate a new IP address depending on the interworking case.

Unit 10 b′, at step S10, initiates the handoff (HO) with unit 10 a′ which, at step S11, initiates the handoff to WLAN 14 through UMTS 12, which is routed between UMTS 12 and WLAN 14, at step S12, and UMTS 12 alerts unit 10 a′ that the handoff process is complete, at step S13. Unit 10 a′, at step S14, alerts unit 10 b′ that the handoff is complete, whereupon services on the WLAN system are resumed between UE 10′ and WLAN 14, at step S15.

FIG. 5 shows another UE-initiated handoff technique utilizing a WLAN broadcast. UE 10′ is similar to UE 10′ shown in FIGS. 3 and 4.

The UE, through unit 10 b′, listens to the broadcast, at step S1, the broadcast of the list of UMTSs available being provided by WLAN 14, at step S2. UE 10′ through unit 10 b′, receives and stores the UMTS frequency list, at step S3, and initiates handoff (HO) by way of a user initiation or, based on signal quality, at step S4, when the HO is initiated, the user selects a preset preference. When signal quality is used as a criteria, a measure of the signal quality is made and HO is initiated when the signal quality achieves a predetermined threshold.

Upon initiation of the handoff, 10 b′, at step S5, causes radio initialization at unit 10 a′. Unit 10 a′, at step S6, starts UMTS service initialization, which includes package switched (PS) attached, packet data protocol (PDP) context and so forth. UMTS 12, at step S7, completes initialization advising unit 10 a′ that initialization is successful. At step S8, UE 10′, through unit 10 b′, initiates the handoff to the UMTS (service continuity). At step S9, the routing of data occurs between WLAN 14 and UMTS 12, whereupon WLAN 14, at step S10, alerts unit 10 b′ that the handoff is completed (and it was successful). Unit 10 b′, at step S11, alerts 10 a′ that the handoff is completed and turns the WLAN receiver off, at step S12, whereupon services are resumed on the WLAN system between UMTS 12 and unit 10 a′, at step S13.

FIG. 6 shows a UE—initiated handoff from a WLAN 14 to an UMTS 12. In this embodiment, UE 10′, through unit 10 b′, initiates a handoff either by the user or automatically, due to signal quality, at step S1, the procedures herein being substantially identical to those described in connection with step S4 in the embodiment of FIG. 5.

Unit 10 b′, at step S2, causes radio initialization at 10 a′ which, at step S3, locks onto the UMTS system 12, and performs UMTS service and initialization, which step is substantially identical to step S6 shown in the embodiment of FIG. 5. Thereafter, steps S5 through S11 of FIG. 6 which are substantially identical to steps S7 through S13, respectively shown in FIG. 5, are performed, the difference between the embodiments of FIG. 5 and FIG. 6 being that there is no WLAN broadcast in the embodiment of FIG. 6.

FIG. 7 shows a UMTS system initiated handoff from a UMTS 12 to WLAN 14, the handoff technique being power based.

UE 10′, through unit 10 a′ listens to the broadcast channel (BCCH) at step S1, UMTS 12 broadcasting a list of WLANs available, at step S2. UE 10′, through unit 10 a′, receives and stores the WLAN frequency list, at step S3 and, at step S4, initializes the radio unit at 10 b′ providing the frequency list to unit 10 b′, at step S5. The WLAN receiver, at unit 10 b′, monitors the WLAN channels, at step S6, providing a measurement report to unit 10 a′ at step S7, which report is relayed from unit 10 a′ to UMTS 12, at step S8.

UMTS 12, at step S9, targets a specific WLAN and initiates the handoff process, providing the target WLAN system of the handoff process to unit 10 a′, at step S10.

UE 10′, through unit 10 a′ alerts unit 10 b′ of the target WLAN system and the WLAN receiver of unit 10 b′ locks onto the WLAN channel of the target WLAN system, at step S12 and communicates with WLAN 14 to initiate the WLAN service, at step S13.

WLAN 14 authenticates UE 10′ through communication with UMTS 12, at step S14 and, at step S15, grants access by communicating with unit 10 b′ which, at step S16, alerts unit 10 a′ that the handoff is complete. Unit 10 a′, at step S17, alerts UMTS 12 that the handoff to WLAN 14 is complete, whereupon UMTS 12 routes data to WLAN 14, at step S18. UMTS 12, at step S19, advises unit 10 a′ that the handoff process is complete, whereupon, unit 10 a′, at step S20, advises unit 10 b′ that the process is complete, whereupon service on the WLAN system between UE10′ and 14 takes place, at step S21. 

What is claimed is:
 1. A method for use in a user equipment (UE), the method comprising: the UE communicating data via a cellular access network using a first Internet Protocol (IP) address; the UE sending a request message via the cellular access network, the request message indicating a request for information related to access networks available for handoff; the UE receiving a network information message via the cellular access network, wherein the network information message is responsive to the request message and indicates a plurality of wireless local area networks (WLANs) available for handoff; the UE selecting a WLAN from the plurality of WLANs for handoff based on the network information message; the UE performing a handoff from the cellular access network to the selected WLAN; and the UE communicating data via the selected WLAN using a second IP address.
 2. The method of claim 1, wherein the selecting the WLAN for handoff is further based on a user preference.
 3. The method of claim 1, wherein the selecting the WLAN for handoff is further based on a received signal power level.
 4. The method of claim 1, wherein the network information message further indicates a location of each of the WLANs.
 5. The method of claim 1 wherein the request message indicates a request for information related to access networks available for handoff in an area close to the UE.
 6. The method of claim 1, wherein the sending the request message is performed based on a user preference.
 7. The method of claim 1, wherein the network information message indicates coordinates of each of the WLANs.
 8. The method of claim 1, further comprising: receiving information via the WLAN that indicates the second IP address.
 9. A user equipment (UE) comprising: a first transceiver configured to: receive a service via a cellular access network using a first Internet Protocol (IP) address; send a request message via the cellular access network, the request message indicating a request for information related to access networks available for handoff; receive a network information message via the cellular access network, wherein the network information message is responsive to the request message and indicates a plurality of wireless local area networks (WLANs) available for handoff; and a processor configured to select a WLAN of the plurality of WLANs for handoff based on the network information message; and a second transceiver configured to: perform a handoff from the cellular access network to the selected WLAN; and communicate data via the selected WLAN using a second IP address.
 10. The UE of claim 9, wherein the processor is configured to initiate the handoff further based on a user preference.
 11. The UE of claim 9, wherein the processor is configured to initiate the handoff further based on a received signal power level.
 12. The UE of claim 9, wherein the network information message further indicates a location of each of the WLANs.
 13. The method of claim 1 wherein the request message indicates a request for information related to access networks available for handoff in a cell serving the UE.
 14. The UE of claim 9 wherein the request message indicates a request for information related to access networks available for handoff in a cell serving the UE.
 15. The UE of claim 9 wherein the request message indicates a request for information related to access networks available for handoff in an area close to the UE.
 16. The UE of claim 9, wherein the first transceiver is configured to send the request message based on a user preference.
 17. The UE of claim 9, wherein the network information message indicates coordinates of each of the WLANs.
 18. The UE of claim 9, wherein the second transceiver is further configured to receive information via the WLAN that indicates the second IP address.
 19. A method for use in a user equipment (UE), the method comprising: the UE communicating data via a cellular access network using an Internet Protocol (IP) address; the UE sending a request message via the cellular access network, the request message indicating a request for information related to access networks available for handoff; the UE receiving a network information message via the cellular access network, wherein the network information message is responsive to the request message and indicates a plurality of wireless local area networks (WLANs) available for handoff; the UE selecting a WLAN from the plurality of WLANs for handoff based on the network information message; the UE performing a handoff from the cellular access network to the selected WLAN; and the UE communicating data via the selected WLAN using the IP address.
 20. A user equipment (UE) comprising: a first transceiver configured to: receive a service via a cellular access network using an Internet Protocol (IP) address; send a request message via the cellular access network, the request message indicating a request for information related to access networks available for handoff; receive a network information message via the cellular access network, wherein the network information message is responsive to the request message and indicates a plurality of wireless local area networks (WLANs) available for handoff; and a processor configured to initiate a handoff from the cellular access network to a WLAN of the plurality of WLANs based on the network information message; and a second transceiver configured to: perform a handoff from the cellular access network to the selected WLAN; and communicate data via the selected WLAN using the IP address. 